Ellagic acid from acorn fringe by enzymatic hydrolysis and combined effects of operational variables and enzymes on yield of the production

The individual effects of three different enzyme types -- one single enzyme (ellagitannin acyl hydrolase) and two combinations of enzymes (ellagitannin acyl hydrolase-beta-glucosidase-polyphenol oxidase and ellagitannin acyl hydrolase-cellulase-xylanase) -- on ellagic acid yield, combined with other process parameters -- enzyme concentration, hydrolysis time, particle size and solid-to-liquid ratio -- were evaluated by response surface methodology. The selection of the enzymes for the study was based on preliminary experiments that showed higher increments in ellagic acid yield. The quantitative parameters studied were enzyme concentration (0.1, 0.45, 2 w/w or %), solid-to-liquid ratio (0.05, 0.15, 0.2), particle size (220, 445, 900 microm) and hydrolysis time (60, 89, 132 min). Experimental data for ellagic acid yield obtained with a single enzyme and two combination enzymes correlated very well with process parameters (P<0.0001), resulting in models with high coefficient of determination for ellagic acid yield (r(2)=0.9636). The combinations of enzymes appeared more effective for ellagic acid production than the single enzyme did. The yield of ellagic acid from non-heat-treated acorn fringe by the use of enzymes in general increased, compared with that from heat-treated material. The research opens a technological-efficient way and develop easily-available renewable raw material for ellagic acid production.